The Commercial Heat Pump Retrofit Revolution


Published: 31 March 2021

As we now enter this period where the decarbonisation of heat within commercial scale applications, Garry Broadbent MInstR from Pure Thermal shares his views on the quickening pace of heat pump use. Especially where the capacity and higher temperatures available means that heat pumps can now be considered as a definite retrofit option.

The transition to low carbon electricity generation within the UK seems to have happened over an extremely short period. We are now regularly seeing carbon intensity figures for electricity generation of circa: 200gCO2/kWh

A dramatic increase in the application and use of clean electricity generating systems in the form of wind and solar has made a real impact over a very short space of time. It’s reducing carbon intensity levels from over 500gCO2/kWh less than ten years ago.

Clean electricity generation means that industry and commerce now have an opportunity to use this low carbon power in ways that may not have been practical or attractive a few years ago. Particularly where electricity contained a much higher level of carbon content.

Nowhere is this more relevant than where the application of commercial heat pumps is concerned. It is clear that if we have cleaner electricity then heating via electricity will be less carbon intensive than it would have been even a few years ago. A heat pump is the most efficient means of using this low carbon electricity to produce heat, therefore a definite retrofit opportunity has been created to increase carbon efficiency within commercial scale applications.

Cleaner input power

In summary; a commercial heat pump would historically have had difficulty competing with a fossil fuel boiler based on carbon intensity.  But, now the application of heat pumps can make real sense based on the use of cleaner input power.

The result of this is that the application scope for heat pumps has widened significantly and this is particularly relevant where commercial and industrial retrofit applications are considered.

Perhaps the title of this piece is a touch dramatic but if we take revolution as its dictionary definition meaning a ‘sudden change’ then we could definitely say that this is the case where heat pumps are concerned.                                                                                                                                                        

Perceptions and ideas are quickly changing. This is based on the ability of 80C single stage high temperature capable heat pumps that are now able to operate on a straightforward retrofit basis within existing heating and hot water systems. Therefore, it is clear that the opportunity to utilise heat pumps within existing commercial buildings on a retrofit basis offers real potential to reduce carbon and importantly utilise clean electricity.


So, this leads us directly into the question of retrofit heat pump use and can these units be practically applied in this way?

Any heat pump advocate would recommend that, in a perfect scenario, a commercial heat pump system be designed to operate as far down its output temperature curve as possible in order to create the highest levels of efficiency.

However, we must consider that it is not practical to work on a 45°C or 55°C maximum flow temperature basis within most commercial retrofit applications during peak load periods.

Therefore, a heat pump system must be considered that is capable of delivering flow temperatures of 70°C and above when necessary. This is in order to widen the scope of heat pump application within both commercial and industrial sectors.

Heat Pump only vs Hybrid

Several retrofit application options are available on either a ‘Heat Pump Only’ or ‘Heat Pump Boiler Hybrid’ basis. Each option can be configured to maximise value and efficiency to match the needs of the particular application using Heat Pumps that are designed to operate with output temperatures to 80°C and above.

The base line with regard to any commercial retrofit application is that to modify the existing heating system infrastructure within a building can be impractical. For this reason, a heat pump that can operate at the same flow temperature and conditions as an existing fossil fuel boiler can be an ideal solution where high temperatures are needed to meet peak load demands.

This higher temperature capability provides a way to utilise heat pumps via very straightforward integration within an existing heating or hot water system on a fixed temperature or variable temperature weather/compensated basis.

As an example; the OHT air-source range provided by Pure Thermal delivers 80°C high temperature capability with a low global warming potential (Low GWP) refrigerant-based system.                                        

The Pure Thermal Application Team commented that they are regularly providing heat pump selections that are capable of operating with 75°C output flow temperatures where a heat pump is required to be integrated within a heating system that has an existing boiler.

They also noted, interestingly, that many of the systems are hybrid where a boiler is used to operate alongside the high temperature heat pump in ambient temperatures below for example 3°C.

This reduces the required heat pump capacity and its capital cost whilst importantly enabling the high temperature capable heat pump to provide primary heating duty for the bulk of the heating season with the most efficient performance levels.

This hybrid method of operation enables the highest levels of carbon reduction to be achieved alongside reduced heat pump capital costs.

It is interesting to note that these high temperature capable heat pump ranges have the ability to deliver upwards of 900kW heating capacity in a single system with an 80°C output flow which is a real step change from how Heat Pumps have been conventionally viewed.

In summary the capacity and higher temperatures available means that Heat Pumps can now be considered as a definite retrofit option. Especially, as we now enter this period where the decarbonisation of heat within commercial scale applications is a rapidly developing priority.